Not All Camouflage Is Equally Effective

From military personnel to potential prey, camouflage has proven to be an effective way to evade detection. However, a new study from the University of Exeter has found that some ‘predators’ can learn to read certain types of camouflage more easily than other types.

Using human volunteers as their ‘predators’ in a video game-like simulation, study researchers discovered that high contrast markings on virtual moths, similar to the markings on a zebra or giraffe, worked best at the start of the experiment. However, the predators quickly learned to see past these markings and locate prey faster than they were able to find moths with background-matching, low-contrast camouflage, like that of a stick insect or leaf bug, according to the researchers report in the journal PLOS ONE.

Surprisingly, study predators had more difficulty learning how to spot prey with camouflage that included a single white marking than prey with background-matching camouflage. The team theorized that other bright isolated markings seen in the background may lead predators to false-positive detections.

“In contrast, when markings are genuinely conspicuous and beyond the background range then they have short detection times overall and are either easy to learn or there is no benefit to learning as they stand out clearly from the background already,” the researchers wrote. “In accordance with this, we did not find any benefit in learning rates for the targets with green markings and in terms of overall detection they were either neutral or costly.”

Study author Jolyon Troscianko, a biologist at the University of Exeter, noted that the study was unique in its approach.

“This is the first time that a study has focused on the learning of different camouflage types rather than how quickly camouflage prevents initial detection,” he said.

“We found considerable differences in the way that predators learn to find different types of camouflage,” Troscianko continued. “If too many animals all start to use the same camouflage strategy then predators are likely to learn to overcome that strategy more easily, so prey species should use different camouflage strategies to stay under the radar. This helps to explain why such a huge range of camouflage strategies exist in nature.”

The researchers said camouflage provides a striking visual example of how natural selection operates in the grand scheme of evolution. Successful camouflage strategies allow organisms to evade predation and reproduce – ultimately allowing for the proliferation of successfully camouflaged offspring. Camouflage is probably the most common way of avoiding predation in nature, the researchers said.

In their conclusion, the team theorized that high-contrast camouflage has remained effective due to factors limiting predator-prey interactions, thereby keeping predators from successfully reading through this type of camouflage.

“High contrast markings should be favored when predators have limited opportunities to repeatedly encounter the same prey types, for example, in comparatively rare species with short-lived predators, in animals with many predator species, or where predators encounter many prey types,” the researchers wrote. “Conversely, high contrast markings would be costly when species face more specialist long-lived predators, or are highly abundant.”

“An important question for the future is at what point the benefit of high contrast to disruptive markings is lost,” they added.